linux-kernel - Re: [PATCH v1 3/9] powercap: intel_rapl: Use GENMASK() and BIT() macros

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Message-ID: <20260129215225.33cce6dc@pumpkin>
Date: Thu, 29 Jan 2026 21:52:25 +0000
From: David Laight <david.laight.linux@...il.com>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Daniel Lezcano
 <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, Lukasz Luba
 <lukasz.luba@....com>, Srinivas Pandruvada
 <srinivas.pandruvada@...ux.intel.com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/9] powercap: intel_rapl: Use GENMASK() and BIT()
 macros

On Thu, 29 Jan 2026 10:36:40 -0800
Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:

> Replace hardcoded bitmasks and bit shift operations with standard
> GENMASK(), GENMASK_ULL(), BIT(), and BIT_ULL() macros for better
> readability and to follow kernel coding conventions.
> 
> No functional changes.

Assuming that changing values to 'unsigned long' doesn't have any
subtle side effects.

...
>  	value = (ra.value & ENERGY_UNIT_MASK) >> ENERGY_UNIT_OFFSET;
> -	rd->energy_unit = ENERGY_UNIT_SCALE * 1000000 / (1 << value);
> +	rd->energy_unit = ENERGY_UNIT_SCALE * 1000000 / BIT(value);

That should really be:
	rd->energy_unit = ENERGY_UNIT_SCALE * 1000000 >> value;

While using BIT() for bit patterns is resonable, wholesale substition
isn't really right - and that isn't a bit pattern.

	David